Apparatus for translating electrical energy into sound waves



Feb. 8, 1927.

w. J. HERDMAN APPARATUS FOR TRANSIJATING ELECTRICAL ENERGY INTO SOUND WAVES 2 Sheets-Sheet 1 Original Fiked Jan.9, 1924 //\/\/ENTOR Feb. 8, 1927.

w, J. HERDMAN APPARATUS FOR TRANSLAT ING ELECTRICAL ENERGY INTO SOUND WAVES 2 Sheets-Sheet 2 Original Filed Jan.9. 1924 Patented Feb. 8, 1927.

UNITED STA 1,616,620, rss PATENT OFFICE.

. WILLIAM J. HERDMAN, or TORONTO, ONTARIO, CANADA.

APPARATUS Ton TRANSLATING ELECTRICAL ENERGYINTO s'ouim wAvEs- Application'filed January 9, i924, Serial No. 685,147. -Renewed March 2, 1925.

My invention relates to apparatus for translating electrical energy into sound waves, and pertains specifically to that class of such apparatus generally known as loud speaking telephone receivers.

The principal objects contemplated by-my invention comprise producing-a loud speaking receiver, which, while being of the sim-.. ple electro-magnetic type, is capable of util- In the drawings which accompany and.

form a part of this specification, and in which like reference numerals designate corresponding parts throughout:

'Fig. 1 is a planview of one embodiment of my device.

Fig. 2 is a partially sectioned elevation of the same, a quarter of which is full sectioned'on the line AA of Fig. 1, and the remaining section of which is partially sectioned on the same line.

Fig. 3 is a sectional elevation of the same taken on the line BB of Fig. 1.

Fig. 4 is an enlar ed sectioned detail of the annular ridge an annular groove. I v

Referring now to the figures, my device comprises a supporting base 10, preferably turned'of yvood iii the shapeshown in the figures. *The central portion of the base is provided with asubstantially hemispherical recess or aperture 11 designed to contain and partially house the operating elements of the loud speakerf A cover 12 is preferably formed'of brass or other suitable material, and is adapted to be attached to the base 10 by means of screws 13 as shown. The cover 12- serves to support and also to, in conjunction with the base, completely house the operating 'portions of the loud speaker. These operating elements .comprise an upper diaphragm clamp 14, preferably composed of brass and providedwith' a centrally disposed integral socket adapted to receive and support a horn or other acoustic amplifying outlet 16. The socket is provided witha central aperture of substantially equalin'ternal diameter to the internal diameter of the stem of the horn 16. The clamp 14 is further provided with four threaded bosses 17, which permit of the operating elements being attached to the cover 12 by means of screws 18, and is provided with an annular sound chamber 19 of smaller internal diameter than a diaphragm 20, which is adapted to be clamped between the upper diaphragm clamp 14 and a lower diaphragm clamp 21. The lower diaphragm clamp21, preferably constructedof brass, is provided with a centrally disposed sound chamber 22, which is of smaller diameter than the diaphragm 20, and the clamp isfurther provided with an internally threaded aperture adapted to receive an externally threaded cup 23, likewise composed of brass or other non-magnetic material. The upper diaphragm clamp .14 and the lower dia-' phragm clamp 21 are adapted to be maintained superposed one on the other by means of screws 25, and dowels 24, as shown in Figs.2and 3. The screws 25 and dowels 24 are disposed with relation to each other as indicated in -Fig. 1.' The upper dia phragm clampv is provided with an annular ridge 26 which is concentric with the re-' cessed sound chamber and disposed near the edge thereof and is adapted to substantially register with an annular groove 27, 1

provided in the lower diaphragm clamp 21,

and likewise concentric with the sound chamber 22. The diaphragm 20 is adapted to be positioned on the lower clamp member 21 by means of the dowels 24, which likewise serve to position the upper diaphragm clamp 14. As the screws 25 are seated, the diaphragm is tensioned due to the action of the annular ridge in forcing the diaphragm to conform to the contour of the annular groove, and as shown by the center lines in Fig. 4, the annular ridge is slightly smaller in mean diameter than the annular groove, so that the central portion of the diaphragm will be stretched or I tensioned, the degree of tensioning depending upon the diameter, thickness and material used, to give the diaphragm a natural period ofabout that of the medium tones of the human voice.

The cup provided with insulated binding posts 28 and 29, towhich are attached the terminals of a pair of operating tungsten magnet steel, and is, of course,

hardened. t

It will be noticed that the cup 23 is provided, as shown'in Fig. 1, with milled flat-s 40. and 41, to produce apertures through which the extension pole pieces 33 and 34 enter the cup to provide a continuous magnetic junction through the pole pieces 32 with the permanent magnet 35. The cup 23 is further provided with a lever 42 to which -is attached a handle 45, the. lever being secured to the bottom surface of the cup 23 by means of screws 43 and 44. As the cup 23 is threaded into the internally threaded opening provided therefor in the lower diaphragm clamp 21, it is obvious that as the lever 42 is rotated, the cup will be moved forward or back in this opening, to position the pole pieces as 32 with respect to their justed to produce optimum quality.

distance from the diaphragm 20. By this means the tone produced may be changed in quality, and the pole pieces may be ad- Also the distances of the pole pieces from the diaphragm may be increased to permit the diaphragm to vibrate through relatively large amplitudes without impinging upon the pole pieces. and thus permit relatively large amounts of energy to be utilized to produce relatively large sound volumes, without oceasioning distortion duetocontact between the diaphragm and the pole pieces. It will be obvious that the cup 23 must thread into the threaded, opening provided therefor accurately, to eliminate the possibility of undesired relative motion be tween the cup and the lower diaphragm member. To this end, the diaphragm clamp is provided with oppositely located slots 46 and 47 which, with the screws 49 and 48, serve as a means for compressing-a thread on the clamp 21 to compensate for deficieneics in manufacture or wear. This is a very important feature, as any undesired relative motion existing between the clamp 21 and the cup 23 will obviously reduce the efficiency of the device.,

It will be noted in Fig. 1 that a portion of the wooden base'near the upper .edge thereof, is cut away to provide an opening 50 to permit of movement of the lever 42.

It will be further noticed that an opening 60 is provided in the base to permit contact, by means of a flexible cord or other conductor, wlth the binding posts 28 and 29.

I find that a noted dimensions, and of about .010 of an inch in thickness, gives remarkably good results, when the diaphragm is tensioned as heretofore mentioned to have a natural pe-' riod of about 500 cycles per second.

While I have thus described one embodiment of my device, it is to be distinctly understood that I may vary the details thereof without departing from the spirit or narrowing the scope of my invention.

' Having thus completely described my invention, what I claim as new and desire to secure by Unit-ed States Letters Patent is as follows 1. In a loud speaking receiver, an upper clamp provided with an acoustic oi1tlet,a lower clamp, anuaperture therein, a diaphragm adapted to be positioned by dowels,

and maintained between said upper and lower clamps, a cup-adapted to be, adjustably maintained in the aperture in said lower clamp, a pair of operating electromagnets maintained within said cup, a pair of extension pole pieces emerging through apertures provided in'said cup, a permanent magnet adapted to be attached to said extension pole pieces, and means whereby said operating magnets carried by said cupmay be moved with relation to said diaphgram.

2. In a loud speaking receiver, an'upper clamp provided with an acoustic opening, a sound chamber and an annular ridge eoneentric with said sound chamber and disposed near the edge thereof; a lower clamp provided with a series of dowels near the outer edge thereof, and further provided with a threaded centrally disposed aperture, a sound chamber and an annular groove disposed concentric with said sound chamber; a diaphragm adapted to be positioned by the dowels in said lower clamp and to be tensionedby the action of said annular tongue and groove when said upper and lower clamps are in normal position; a

threaded cup adapted to be maintained in the centrally located aperture in said lower clamp, a pair of operating electro-magnets maintained centrally within said cup, and adapted to be positioned thereby in relative close proximity'to the central portion of said diaphragm, anda lever attached to said cup whereby said cup may be moved within the opening provided therefor in said -lower clamp, to vary the distance between said operating eleetro-magnets and said diaphragm.

3. In a loud speaking receiver, an upper diaphragm clamp provided with a centrally disposed acoustic opening, a sound chamber disposed concentric with'said acoustic opening, and an annular ridge disposed near the edge "handle and attached to the bottom surface of said sound chamber and, concentric, therewith; a lower diaphragm clamp provided with a centrally disposed threaded aperture, a sound chamber and an annular groove disposed near the edge of said soundchamber and concentric therewith; a diaphragm adapted to be maintained between said upper and lower clamps, and to be formed near the edge thereof by the action of said annular ridge and groove to have its central portion tensioned; an externally threaded cup adapted to be maintained within the threaded aperture in said lower diaphragm clamp;

a pair of operating electro-magnets maintaiued centrally within said cup; extension pole pieces for said magnet emerging through apertures provided therefor in said cup; a permanent magnet maintained without said cup and attached to said extension pole pieces; and a lever provided with a of said cup whereby said cup may be moved relatively with respect to said lower diaphragm clamp to vary the distance betweeni adapted to co-act by the act of clamping said diaphragm between said clamps to tension said diaphragm, a cup adj ustably maintained in the aperture in said lower clamp, a pair of operating electro-magnets maintained within said cup, a pair of extension pole pieces emerging through apertures provided in said cup and a permanent magnet adapted to be attached to said extension pole pieces.

WILLIAM J. HERDMAN.. 

